Mesoscale Discussion 0485 NWS Storm Prediction Center Norman OK 0333 PM CDT Tue Apr 28 2020 Areas affected...eastern Missouri...southeast Iowa...into western Illinois Concerning...Severe potential...Watch likely Valid 282033Z - 282200Z Probability of Watch Issuance...95 percent SUMMARY...Severe thunderstorms with the potential for damaging wind gusts and large hail with a tornado or two will be likely this afternoon and evening. DISCUSSION...Mid-level ascent from an approaching shortwave trough over the central High Plains is impinging on the warm sector of a surface cyclone over southern Minnesota and northern Iowa. Boundary layer moisture has increased through the day across Missouri and southern Illinois with surface dewpoints in the upper 50s into the low 60s F. As a result of the moistening, 1000-2000 J/kg of MLCAPE has developed across the area. The instability is concurrent with effective bulk-shear of 30 to 40 kt. Severe storms including a mix of line segments and a few supercells are likely to develop over the next 1 to 2 hours along the surface trough/cold-front trailing the surface low. Initially, these storms will pose a risk for a tornado or two but will transition to a damaging winds and hail threat.